Brief Reports
Copyright ©The Author(s) 2005. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Nov 14, 2005; 11(42): 6694-6700
Published online Nov 14, 2005. doi: 10.3748/wjg.v11.i42.6694
DNA end binding activity and Ku70/80 heterodimer expression in human colorectal tumor
Paola Mazzarelli, Paola Parrella, Davide Seripa, Emanuela Signori, Giuseppe Perrone, Carla Rabitti, Domenico Borzomati, Armando Gabbrielli, Maria Giovanna Matera, Carolina Gravina, Marco Caricato, Maria Luana Poeta, Monica Rinaldi, Sergio Valeri, Roberto Coppola, Vito Michele Fazio
Paola Mazzarelli, Emanuela Signori, Maria Luana Poeta, Vito Michele Fazio, Laboratory of Molecular Medicine and Biotechnology, Interdisciplinary Center for Biomedical Research, Università Campus Bio-Medico, Rome 00155, Italy
Paola Parrella, Davide Seripa, Maria Giovanna Matera, Carolina Gravina, Vito Michele Fazio, Laboratory of Gene Therapy and Oncology, IRCCS “Casa Sollievo della Sofferenza” Hospital, San Giovanni Rotondo (FG) 71013, Italy
Giuseppe Perrone, Carla Rabitti, Service of Histopathology, Università Campus Bio-Medico, Rome 00155, Italy
Domenico Borzomati, Marco Caricato, Sergio Valeri, Roberto Coppola, Department of General Surgery, Università Campus Bio-Medico, Rome 00155, Italy
Armando Gabbrielli, Department of Digestive Disease, Università Campus Bio-Medico, Rome 00155, Italy
Emanuela Signori, Monica Rinaldi, Vito Michele Fazio, CNR Gene-Medicine Division, Section of Molecular Medicine, Institute of Neurobiology and Molecular Medicine, Rome 00133, Italy
Author contributions: All authors contributed equally to the work.
Supported by Italian Ministero della Salute, IRCCS, RC0302TG13, and by Ministero dell’Istruzione, Università e Ricerca scientifica e tecnologica (MIUR), COFIN2002, to the Università Campus Bio-Medico
Correspondence to: Professor Vito Michele Fazio, Laboratory of Molecular Medicine and Biotechnology, Università Campus Bio-Medico, Via Longoni, 83, Rome 00155, Italy.
Telephone: +39-06-22541780 Fax: +39-06-22541780
Received: February 1, 2005
Revised: April 23, 2005
Accepted: April 26, 2005
Published online: November 14, 2005

AIM: To determine the DNA binding activity and protein levels of the Ku70/80 heterodimer, the functional mediator of the NHEJ activity, in human colorectal carcinogenesis.

METHODS: The Ku70/80 DNA-binding activity was determined by electrophoretic mobility shift assays in 20 colon adenoma and 15 colorectal cancer samples as well as matched normal colonic tissues. Nuclear and cytoplasmic protein expression was determined by immunohistochemistry and Western blot analysis.

RESULTS: A statistically significant difference was found in both adenomas and carcinomas as compared to matched normal colonic mucosa (P<0.00). However, changes in binding activity were not homogenous with approximately 50% of the tumors showing a clear increase in the binding activity, 30% displaying a modest increase and 15% showing a decrease of the activity. Tumors, with increased DNA-binding activity, also showed a statistically significant increase in Ku70 and Ku86 nuclear expression, as determined by Western blot and immunohistochemical analyses (P<0.001). Cytoplasmic protein expression was found in pathological samples, but not in normal tissues either from tumor patients or from healthy subjects.

CONCLUSION: Overall, our DNA-binding activity and protein level are consistent with a substantial activation of the NHEJ pathway in colorectal tumors. Since the NHEJ is an error prone mechanism, its abnormal activation can result in chromosomal instability and ultimately lead to tumorigenesis.

Keywords: Colorectal cancer, Colon adenoma, DNA-dependent protein kinase, Ku70/80 heterodimer, Mismatch repair, Non-homologous end joining, Double strand break repair, Chromosomal instability